The present invention relates to apparatus for making X-ray images, and more particularly to improvements in apparatus wherein latent images of object-modulated X-rays are formed on dielectric receptor sheets while the sheets dwell in the gas-filled interelectrode gap of an ionography imaging chamber. Still more particularly, the invention relates to improvements in means for influencing certain characteristics of dielectric receptor sheets prior to introduction of such sheets into the interelectrode gap of an ionography imaging chamber.